Mature spores have been found only once in North America, in a sporophyte collected in the Wisconsin Dells in July. According to S. M. Hague and W. H. Welch (1951), antheridia are present from March to August, and archegonia are evident from May to August. In spite of the specific epithet, the original collection of this distinctive moss was made in Iceland. Usually bright green, Bryoxiphium norvegicum has on occasion been mistaken for grass seedlings. Bryoxiphium can also be confused with another moss genus, Fissidens. In both genera the leaves are distichously arranged, and the conduplicate (folded lengthwise) portion and weak abaxial lamella of the larger and better developed leaves of Bryoxiphium can be mistaken for the vaginant and abaxial laminae, respectively, of Fissidens. Costal structure of the two genera, however, is quite different, and species of Fissidens, with few exceptions, have a well-developed haplolepidous peristome.

Á. Löve and D. Löve (1953) recognized two subspecies of Bryoxiphium norvegicum, subsp. norvegicum and subsp. japonicum, distinguished by the degree of serrulation on the distal parts of the perichaetial leaves. Within subsp. norvegicum they recognized two varieties, norvegicum and mexicanum (the latter variety recognized at the species level by H. A. Crum in A. J. Sharp et al. (1994), based on differences in the length of marginal cells in perichaetial leaves. According to Löve and Löve, North American populations north of Mexico belong to var. norvegicum, having perichaetial leaves only slightly serrulate and marginal cells much longer than the interior laminal cells. A report of B. norvegicum from Pennsylvania cannot be substantiated.